Apparatus for heat exchange



June 1935- w. c. HARPSTER APPARATUS FOR HEAT EXCHANGE Filed Jan. 6,19.32

||||||I l l l Kirk/4 /.M K\\\ Patented June 25, 1935 UNITED STATESPATENT OFFICE APPARATUS FOR HEAT EXCHANGE ration of Delaware ApplicationJanuary 6, 1932, Serial No. 584,983 2 Claims. (01. 122-235) Thisinvention relates to'improvements in the control of transfer of heatthrough the boundaries or confines of fluid systems. The invention willbe fully understood from the following de- 5 scription taken inconnection with the accompanying drawing in which latter- Fig. 1 is aside elevational view of a heat exchanger unit containing theimprovements.

Fig. 2 is a transverse sectional view taken along the line I[-II of Fig.1.

Referring to Figs. 1 and 2, heat exchange unit is shown comprising twoprimary conduits 2| and 22 which are connected by a secondary conduit23. The secondary conduit 23 constitutes a web which may be perforatedat 24' to form channels or passageways for the furnace gases and topermit greater freedom in expansion of the metallic structure. Theparallel primary conduits 2I-22 constitute a wall having a heatabsorbing face exposed to the interior of the furnace chamber.

The amount of heat imparted to the water or primary fluid within theprimary conduits 2 l22 and also the temperature of the metalconstituting the wall of the primary conduits is regulated by the use ofa secondary fluid medium. The sec ondary fluid medium is passed throughsecondary or auxiliary conduits 23. The secondary conduits 23 may besecured to the primary conduits 2 I-22 by cementing, welding, directfabrication or any method of juxtaposition which will afford control ofheat transfer and temperature of the primary elements. The secondaryconduits may be in any ratio of cross sectional-area with respect to theprimary conduit, may be made of any suitable material and may be in anydesired number with respect to the primary conduit.

By the construction described the primary conduits while directlyexposed to the severe furnace conditions are subjected to a micrometersystem of control of tube metal temperatures through the biasing ordifferential relationship of the two systems. The secondary fluid suchas steam which is passed through the secondary conduits can bemaintained in a system which is entirely independent of the operationfor which the primary fluid is used and is thus variable over a widerange of flow to control the tube metal temperature. of the primarytubes and the rate of heat transfer into the primary fluid.Altematively, the secondary fluid may be a part of the primarycirculation by-passed through the secondary tubes at an accelerated rateand passing through external cooling apparatus, not shown, in order toafford a temperature control of the heating surface which is exposed tosevere furnace conditions. Any required amount of heat may be swept fromthe primary conduit elements by the secondary fluid and returned to thesystem as preheated air, superheated steam or the like. The burning ofthe primary conduit elements is minimized and the efliciency of theoperation is increased by allowing maximum temperatures and minimumexcess of air.

The invention is particularly applicable for building heat transfersurfaces of pipe stills for distilling hydrocarbon oil, for crackingcoils, for subjecting hydrocarbon oil to cracking conditions oftemperature and pressure, and for other oil heating elements. Theprimary conduit such as 2l-22 is utilized for the main operation ofheating the oil as is customary in pipe stills and cracking coils. Thesecondary conduits such as 23 are for the circulation of another fluidsuch as steam for superheating, air for combustion or some other mediumdirectly connected with the primary operation. The circulation throughthe secondary conduits controls radiant heat transfer and allows highheat release in the furnace.

The secondary conduits provide an independent means of controlling tubemetal temperatures which is advantageous to prevent burning of thetubes, to control coke formation and to increase the length of runs oncracking coils. As applied to pipe stills for the distillation ofhydrocarbon oils, the secondary tubes permit of close regulation overthe rate of heat transfer whereby cracking of the less refractory stocksis minimized. When utilized in an oil tube still the control of tubetemperatures by the secondary heating elements permits of combustionwith a small amount of excess air thus increasing the furnacetemperature and raising the thermal efflciency of the operation. Ifdesired, the tubular structure can be used in combining steam generationwith oil still operations by passing water through the secondary tubes.The duplex heat transfer surface functions either as a superheatingsurface or in the direct generation of steam. Also in certain operationsit may be desirable to have the secondary fluid hotter than the primaryto increase rates of heat transfer in certain portions of total surface.

Various changes may be made within the scope of the appended claims inwhich it is desired .to claim all novelty inherent in the invention asbroadly as the prior art permits.

I claim:

1. Heat exchange apparatus, comprising a plu rality of parallel unitsassembled to form a wall having a heat absorbing face, each unitincluding 10 rality ct parallel units assembled to form a wall having aheat absorbing face each unit comprising a primary conduit, and asecondary conduit of relatively small cross sectional area, theadjoining faces of the conduits extending parallel and in direct contactover an extended area transversely with each other, portions of saidface of the secondary conduit being recessed to form channelstransversely of the conduits.

WALTER C. HARPS'IER.

